Main idea with multiple subs is to create lots of different bass modes in different locations. Easiest way to do this is put them all around the room asymmetrically. In other words along the walls but each one a different distance from the corner.
But really, they're not fussy at all. With one sub, that one sub has to be very powerful and put out enough bass, and so the modes it creates are very powerful and the bass is lumpy. You move and listen, move and listen, trying to find the least lumpy spot.
With four subs they all add together so each one has to put out much less bass so the lumps it makes are much less noticeable. They're there, but small. So technically you could go to all the same trouble searching around for the perfect spot for each sub. That's the crawl method- put one in the sweet spot, crawl around listening for the best bass, put one sub there. Repeat for each sub.
I tried doing this. The result was no different than when I put them where they were asymmetrical and worked better with the room. Tim did this, wound up with them almost exactly like I said, near to but different distances from the corners.
Actually if you read my review it raves about how great they sounded when all I did was plop em down no real thought or planning other than near a wall and near a corner- but not equally near. Its one of those rare things in audio where its just super easy to get outstanding results. As long as you have four.
